Addition agent for storage battery paste



,Oct.15,1940. H. B. BIRT'ET AL 2,217,781

ADDITION AGENT FOR STORAGE BATTERY PASTE Original Filed Sept. 2. 193a METHOD it '1. METHOD a 2.

HARDWOOD HARDWOOD SAWDUST I SAWDUST HLTRATE Flu'nm: USCARDED TREAT WITH TREAT WWN DSCARDED MUNERAL ACID QAUSTDQ I I I v RESlDUE RESIDUE TANNINS FROM THI$ POiNT TANNBNSI ZARBOHYDRATES METHODS ARE mng CARBOHYDRATES Susana aueARs RESINS & RESENS 'RESIJDUE 'mscgapgp SULFONATION IN H2503 OR @LDTRDN con-resume FREE 50,,

I v FBLTRATE CELLULOSE g 'EVAPQRATED To APPRoxnMATEw VOLUME FILTRATE l mscARDED PRECIPITATION H 50 ADDED INPURITIES .AND PRECIPITATE msopowvmu LBGNBN SULFONlC ACID- E 2 ALTERNATIVE TREATMENT ADDITION OF H2O vTO D\$5OLVE PREClPITATE NEUTRAUZATION AND PREUPITATlON BY ADDITION OF BAslc SALT I FILTRATE PRECIPITATE DISCARDED UGNIN SULFONIC ACID; Haward 5.51M

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and this application 4 Claims. (cuss-2s sulfonic acidin the substantially pure state yields better results in the battery paste than'can-be btained by the use oi the waste liquorwithout I an addition agent for i use i the manuiacture of storage batter'ypaste and is-particularly concerned with fan addItion'; agent obtained from the chemical treatment of t. I 51;.hardwood'and to themethodoi making said addition agent. s v

i This applica'tionis a division of, our current I September2, 193s. I I An object-of the invention isto providea method: whereby the lignin of hardwood may be sulfonated and then obtained in the substan-.

tially pure state tor-subsequent use in awar battery paste;

Y is a further obiect oi the invention to prov'ide amethod for sulfonating certain desirable constituents in' hardwood and separating these constituents from the remaining constituents of I the wood, such sulionated -.co'nstituents being used as addition agents in the paste of the nega tive battery plate forinhibiting, Orgreatly re- :Jtarding, crystal growth ofjthe-spongelead.

A still further object of the invention is to- I provide an addition-agent to be'incorporated in 1the' paste of thenegative plate oflead storagev batteriesfor inhibiting or substantially preventing the. crystal growth of sponge lead,- said addition agent being extracted irom hardwood and having the'charact'eristicoi increasing the elecvtrlcal capacity of the negative plates at low'ainbient temperatures while not substantially aifecting thedensity oi the plate paste. I

Further objects and advantages-of the present invention as herein disclosedwili become apparent from the following description:. j I

' In the drawing the figure is a flow chart indicating the steps in the processes of obtaining sulfonated hardwood lignins and their salts.

It has heretofore been proposed to utilize ligno I 40 sulfonic acid as an addition agentlfor-the negative plate paste of lead storage batteries. Such ligno sulfonic acid has either been usedin the combined state with various other ingredients or in a substantially pure state, and in both instances has been a product obtained-from waste sulfite liquor of the paper mills. This waste sulfite liquor is obtained from the digestion of coniferous woods such as hemlock and spruce, etc.,

with solutionsioi calcium 'bi-sulflte and/or sulfurous acidp By this process the cellulose is separated from the remaining constituents. of

wood and is used in the manufacture of paper while the waste liquor is'aj-byeproduct and as herein explained is often used for abattery paste addition agent. It has been found that ligno pendingjapplieation no. $28.18; A

purification.

The present invention is uponzfthejdisg covery that the sultonatedprodu'cts oi the lign'ins of hardwood'ha've highly superiorreactions a's ad-- dition agents in storage battery paste over the lignins of soft or coniferous woods asheret'oi'ore utilized. While muchresearch has beenccarrled -10 on ligninsoi coniferous woodthere has been but very little investigation into thechara'cteristics v of. the lignins oi hardwoods. In the descriptivematter o1 thh invention we will refer to the s'ulfonated lignins of hardwood as'lignin sulfonic' l5 acid... differentiated from ligno sulionic acid,

.the sulionat'ed product of the lignins of coniier- 'ous woods.

It has been found that lignin sulfonic acid in very small quantities; for examplefrom '.02% to 20 1% when added to the negative'plate pasteoi lead storage batteries substantally prevents crystal growth of sponge lead in the negative plate; I

We have further found that lignin sulfoniclacid has ahigher degree of eil'ectiveness for increas- 2 5 ing the electrical capacity; at low ambient ,tem--" peratures. of the negative plate than ,anyoi the addition agents heretofore proposed.- Furthermore, lignin sulfonic acid is less soluble in water or acids and has a higher degree of stability to ;30

.the efi'ect of heat than has ligno sulionic a'cidas-v made from coniferous woods.

Our discovery of the many beneficial effectsobtained through the use of lignin sulfonic .aeid makes possible the productionof an' improved storage battery plate having high. electrical capacity over a wide rangeof temperatures and which is not deteriorated by crystal growth of sponge lead therein. 5

-It has been found ,by actual tests'that a bat- 40 I teryQincluding hardwood lignin sulfonicacid, as

' an addition agent to the negative plate paste, has 10% greater electrical capacity at 0 F. than asimilar type battery tested under identical conditions but utilizing ligno sulionic acid from 45 coniferous woods as the addition agent. This improvement in operating characteristics'is even further amplified. by the fact that the-second mentioned battery had 7% by. weight more material onthe negative plates. j X-ray analyses on negative plates conclusively show that the lead particles therein have a constant. growth when no agent is used, such growth gradually deteriorating the plate and lessening its electrical capacity. when lignin sulionic acid is 55 used as an addition agent, in varying small percentages the growth of the lead crystals is inhibited 'and substantially prevented throughout the life of the battery plate. x-ray analyses also show that small additions of ligninsulfonic acid substantially prevent crystal growth of the lead sulfate crystals as produced by the discharge of the plates during operation of the battery.

The sulfonated lignins of hardwood as hereintofore mentioned have improved characteristics over the sulfonated lignins of soft wood. Weattribute this increase in eflectiveness to the fact that th lignins have a different structure than the lignins of soft wood, which structural difference carries over into the sulfonated product thereof and thus causes the hardwood lignin sulfonic acid to have different and improved chemical properties over ligno sulfonic acid as derived from coniferous woods.

The preferred method of making lignin sulfonic acid is as follows: 10 lbs. of hardwood, for example red oak, beech, aspen, maple, etc., sawdust, is boiled for a period of three hours in 7 gallons of a Weak mineral acid solution, preferably 3% sulfuric acid solution. Phosphoric, hydrochloric or nitric acid may be used, but their use requires exacting control procedure which is unnecessary when using sulfuric acid. This treatment dissolves out the sugars, tannins, carbohydrates and resins which occur as constituents of the wood. This mixture is filtered and the insoluble residue which amounts to about 7 lbs. is washed, the filtrate usually about 25% by weight of the sawdust used, is discarded. The insoluble residue consisting substantially of cellulose and lignin is next digested in 4 gallons of a solution containing free S02, or in a sulfurous acid solution or by any other well known method, under 60 lbs. per

square inch pressure and for a period of approximately 12 hours. This digestion causes the sulfonation of the hardwood lignin rendering it soluble, while the cellulose remains substantially insoluble. residue is discarded. The filtrate consists of about 4 gallons of hardwood lignin sulfonic acid in a concentration of about 7 /2%. This solution also contains a small quantity of hemi-celluloses which are rendered soluble by the sulfonation process. The filtrate is preferably evaporated to approximately its original volume or two gallons, and to this solution is added two gallons of 40% sulfuric acid solution. The resultant mixture will therefore contain about 25% sulfuric acid which brings the acidity of the solution sufficiently high to precipitate the greater part of the lignin sulfonic acid. The solution is filtered and the precipitate is washed with 20% sulfuric acid solution in which it is insoluble. The filtrate is discarded.

The precipitated lignin sulfonic acid amounts to approximately 2' lbs. and can be mixed directly in the negative plate paste, or in the preferred form, is dissolved in water and the water solution thereof is added to the negative paste. Usually 0.2% to 0.3% by weight of lignin sulfonic acid gives the optimum results in battery performance although greater amounts may be used. An alternative method of adding the material to the paste is to immerse the dried negative plate (before formation) in a 10% water solution of hard- The mixture is filtered and the cellulose wood lignin sulfonic acid in which instance the plate paste absorbs the lignin sulfonic acid to provide substantially similar results.

An alternative method oi removing sugars, tannins, carbohydrates and resinsfrom' the hardwood sawdust is to use 10 gallons of caustic solution, preferably a 1% sodium hydroxide solution for each 10 lbs. of hardwood sawdust, and treat the sawdust therein for a period of 15 hours at room temperature. After filtering and washing the residue undergoes a procedure similar to that hereinbefore described.

Another modification in the use of the addition agent is to chemically react the hardwood lignin sulfonic acid with a basic salt such as a metal hydroxide whereupon sulfonates are formed. For example. barium hydroxide may be used or any other hydroxide of the alkaline earth metals, or oxides or hydroxides of the heavy metals preferably lead. Preferably barium hydroxide is added to an aqueous solution of hardwood lignin sulfonic acid at room temperature and in quantities suflicient to neutralize the solution. This procedure causes precipitation of the barium salt of lignin sulfonic acid which makes an excellent agent in accordance with the procedure outlined herein, that such an addition agent does not increase the density or weight of the plate paste and is therefore highly desirable therein.

While specific quantities and concentrations'oi ingredients have been specified throughout the description of chemical process used in forming hardwood lignin sulfonic acid, such quantities and concentrations are not limiting, but are merely set forth for illustrative purposes. Variation in the quantities and concentrations of the ingredients may be made without departing from the spirit of our invention so long as the desired results are obtained.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A battery plate paste including as an addition agent a sulfonated acid product of hardwood 

